The then() method of Promise instances takes up to two arguments: callback functions for the fulfilled and rejected cases of the Promise. It stores the callbacks within the promise it is called on and immediately returns another Promise object, allowing you to chain calls to other promise methods.

The find() method of Array instances returns the first element in the provided array that satisfies the provided testing function. If no values satisfy the testing function, undefined is returned.

The Symbol.toPrimitive static data property represents the well-known symbol Symbol.toPrimitive. All type coercion algorithms look up this symbol on objects for the method that accepts a preferred type and returns a primitive representation of the object, before falling back to using the object's valueOf() and toString() methods.

An iterator able to yield elements from both ends.

An iterator which, starting from an initial item, computes each successive item from the preceding one.

A range only bounded inclusively below (`start..`).

The entries() method of Map instances returns a new map iterator object that contains the [key, value] pairs for each element in this map in insertion order.

An iterator over the non-ASCII-whitespace substrings of a string, separated by any amount of ASCII whitespace.

The set() method of Map instances adds a new entry with a specified key and value to this Map, or updates an existing entry if the key already exists.

The length data property of an Array instance represents the number of elements in that array. The value is an unsigned, 32-bit integer that is always numerically greater than the highest index in the array.